Metering pumps may be piston pumps or diaphragm pumps and are often used to continuously apply measured quantities of liquid into other material being conveyed. For instance, seeds are treated with chemicals which must be very accurately measured for the correct effect.
Such seed may be conveyed by a screw conveyor and small measured quantities of chemical may be applied to the seed being conveyed by the screw auger. The metering pump may be operated in close coordination with the auger shaft.